Direction reversing control for a machine control system

ABSTRACT

A machine control system, such as a control for a paper cutting machine, is provided for purposes of reversing the direction of travel of a movable member, such as a back gauge in a paper cutting machine, driven by a reversible motor between forward most and rearward most positions relative to a work station. A control record has two spaced marks recorded thereon for defining the forward most and rearward most positions. A mark sensor serves to sense the marks and in response to each mark provides a reverse signal pulse. Relative motion is provided between the control record and the sensor proportional to the velocity of the movable member. A memory is actuated to one of two stable states in dependence upon the direction the movable member is traveling when a reverse mark is sensed. The commanded condition of the memory together with the occurrence of a reverse signal pulse generated in response to the sensed reverse mark, causes the motor to reverse and drive the movable member in the opposite direction. In addition, circuitry is provided to prevent the motor from reversing in response to a reverse mark when the movable member is traveling in a backward direction until a position command signal, also recorded on the control record, is sensed by a second sensor.

United States Patent Foley et al.

[ 51 June 20, 1972 DIRECTION REVERSING CONTROL FOR A MACHINE CONTROLSYSTEM Richard G. Foley, Dayton; James E. Murray, University Heights,both of Ohio inventors:

Assignee:

US. Cl.... ...3l8/l62, 318/567 Int. Cl. ..G05b 19/02 Field of Search ..318/158, 272, 443, 444, 600,

[56] References Cited UNITED STATES PATENTS l0/l96l Gough, Jr. ..3l8/5743/1962 Myska 7/1965 Fielder et al ..3 [8/600 X Primary Examiner-HaroldBroome Assistant Examiner-W. E. Duncanson, Jr. AttorneyYount and Tarolli[57] ABSTRACT A machine control system, such as a control for a papercutting machine, is provided for purposes of reversing the direction oftravel of a movable member, such as a back gauge in a paper cuttingmachine, driven by a reversible motor between forward most and rearwardmost positions relative to a work station. A control record has twospaced marks recorded thereon for defining the forward most and rearwardmost positions. A mark sensor serves to sense the marks and in responseto each mark provides a reverse signal pulse. Rela tive motion isprovided between the control record and the sensor proportional to thevelocity of the movable member. A memory is actuated to one of twostable states in dependence upon the direction the movable member istraveling when a reverse mark is sensed. The commanded condition of thememory together with the occurrence of a reverse signal pulse generatedin response to the sensed reverse mark, causes the motor to reverse anddrive the movable member in the opposite direction. In addition,circuitry is provided to prevent the motor from reversing in response toa reverse mark when the movable member is traveling in a backwarddirection until a position command signal, also recorded on the controlrecord, is sensed by a second sensor.

17 Claims, 5 Drawing Figures DIRECTION REVERSING CONTROL FOR A MACHINECONTROL SYSTEM This invention relates to the art of machine controlsystems and, more particularly, to improvements for reversing thedirection of travel of a movable member, such as a back gauge in a papercutting machine, in dependence upon command marks recorded on a controlrecord.

The invention is particularly applicable for use in conjunction withcontrolling the direction of movement of a back gauge in a paper cuttingmachine; however, it is to be appreciated that the invention is notlimited thereto as it may be employed in various machine tool systemswherein it is desired to control reversing movement of a movable memberrelative to a work station.

Paper cutting machines typically comprise a worktable upon which a backgauge is slideably movable for purposes of positioning a pile ofmaterial, such as paper, to be cut by a guillotine type cutting tool.The positioning of the back gauge, and, hence, the pile of material tobe cut, is controlled pursuant to a cutting program typically recordedas magnetic or optical marks on a control record. More than one cuttingprogram may be recorded on the control record with each program havingposition command marks as well as direction reverse marks respectivelyrecorded on different channels. Several position command marks may berecorded for a particular program whereas usually only two directionreverse marks are recorded respectively representative of the beginningand ending boundaries of the program. The beginning boundary, forexample, may be representative of the rearward most limiting position ofthe back gauge with the ending boundary being indicative of the forwardmost limiting position of the back gauge as it travels relative to thecutting tool. As the back gauge is being advanced toward the cuttingtool it is periodically decelerated to a stop condition in response to aposition command mark being sensed by a position sensor. A cuttingoperation is then performed and the back gauge may be further advancedtoward the cutting tool. The back gauge will be stopped in dependenceupon the number of position command marks recorded for the particularcutting program. In some systems two position sensors are employed, oneknown as a deceleration sensor and the other being known as a stopsensor. Each position mark is sequentially sensed first by thedeceleration sensor for purposes of decelerating the back gauge from ahigh speed to a low speed, and then by the stop sensor for deceleratingthe back gauge from the low speed to a stop condition so that a cuttingoperation may be performed.

As the back gauge is advanced toward the cutting tool both the positioncommand sensor, as well as the reverse command sensor, operate to sensemarks recorded in the respective position and direction channels.Normally, after all of the position command marks have been sensed theback gauge is reversed in its direction of travel in response to atrailing forward most direction command mark being sensed by the reversesensor. The back gauge as well as the control record, in a system wherethe sensor is held stationary and the control record and back gauge aremoved either at the same velocity or at proportional velocities, arethen driven by a motor in a backward direction relative to the cuttingtool until the reverse sensor senses a rearward most direction commandmark. This causes the back gauge to be advanced in the forwarddirection. The momentum of the back gauge will cause it to over travelthe forward most and rearward most travel limits and, consequently, thereverse mark that commanded the back gauge to reverse its direction oftravel will again be seen as the back gauge commences to travel in theopposite direction. Proposals have been made to incorporate a time delayonce a reverse mark has been sensed to prevent the direction reversingsystem from operating until the back gauge has had sufficient time toretraverse the normal over travel distance experienced when itsdirection of travel is reversed. This will prevent the back gauge frombeing immediately reversed back to its earlier direction of travel uponthe mark being again sensed by the reverse sensor. However, considerabletime is lost if the reversing system is delayed for this period of time.Consequently, it is desirable to provide control circuitry forcommencing the reversing operation upon sensing of a reverse commandmark while at the same time inhibiting the sensor circuitry fromproviding two reverse signals for the same reverse mark.

After the back gauge has traveled from its rearward most to forward mostpositions so as to complete a cutting program recorded on the positionchannel, a reverse mark is sensed in the direction channel to cause theback gauge to be driven in a backward direction. Frequently it is atthis point that the operator may desire to use a different cuttingprogram. The position and direction sensors are then shifted laterallyof the control record so as to respectively sense position command marksand reverse command marks in different channels from that of theprevious cutting program. Ifthe forward most limiting marks in thevarious direction channels are not aligned, then when the reverse sensoris positioned to sense direction command marks in a new channel, thefirst reverse mark sensed, while the control record is moving in itsbackward direction, could well be the forward most limiting mark for thenew program. The reversing system would, however, respond to the reversecommand mark to drive the back gauge to a trapped position forwardly ofthe desired forward most position for the new program. It is for thisreason that the forward most limiting reverse marks are normallyrecorded in lateral alignment on a control record. This, of course, willcause the back gauge to be driven to the same forward most position foreach program independently of the number of cutting operations to beperformed. Also, considerable time may be required for recording a newprogram to assure that the forward most limiting marks are in alignment.It is desirable, therefore, that means be provided so that these forwardmost limiting marks need not be in alignment while at the same timepreventing the reversing circuitry from advancing the back gauge in aforward direction when the reverse sensor head senses the forward mostlimiting reverse mark on the direction Control channel for the newprogram.

The present invention contemplates that a machine control system beprovided and which serves to control movement of a movable member, suchas a back gauge in a cutting machine, driven by a reversible motor ineither a forward or backward direction relative to a work station, suchas a cutting tool, and between forward most and rearward most positionsin dependence upon an operating program which includes both positiondefining command marks and direction reverse command marks respectivelyrecorded on different channels of a control record.

In accordance with one aspect of the present invention, the controlrecord includes two spaced marks recorded thereon for defining theforward most and rearward most positions. A mark sensor is employed forproviding a reverse signal pulse in response to each mark sensed.Relative motion is imparted between the control record and the sensor independence upon the direction of travel of the movable member. Adirection memory is provided with input and output circuits togetherwith a trigger pulse receiving circuit and exhibits the characteristicof being actuated by a received trigger pulse to first and second stablestate output circuit conditions in de pendence upon first and secondinput circuit conditions existing when a trigger pulse is received. Atrigger pulse is applied to the memory for each reverse signal pulse. Adirection command circuit is controlled by the memory to, in turn,control the reversible motor to drive the movable member in the backwarddirection when the memory is actuated to its first output circuitcondition. and in the forward direction each time the memory is actuatedto its second output circuit condition. Memory conditioning circuitry isprovided for conditioning the memory input circuit to the secondcondition when the member is traveling in the backward direction, and tothe first condition when the member is traveling in the forwarddirection.

In accordance with another aspect of the present invention, the controlrecord includes a position channel having position command marksrecorded thereon to define desired positions of the movable memberrelative to the work station, and a direction channel having twodirection reverse command marks recorded thereon at spaced locationsdefining the beginning and ending boundaries of a program. Both aposition mark sensor and a reverse mark sensor are provided forrespectively sensing the position and reverse marks and providing foreach respectively sensed mark a position signal pulse and a reversesignal pulse. Relative motion is imparted between the control record andthe sensor means in dependence upon the forward and backward directionof travel of the movable member relative to the work station. A reversecontrol circuit normally responds to each reverse signal pulse forcontrolling the motor to reverse the direction of travel of the movablemember. An indication is provided representative that a sensed reversemark commanded the member to be changed in its direction of travel fromthe forward direction to the backward direction. A control circuit isresponsive to the indication to prevent the reverse control circuit fromresponding to a reverse mark while the member is driven in the backwarddirection until a position mark is sensed by the position sensor.

The primary object of the present invention is to improve the accuracyof positioning and reversing the direction of movement of a movablemember relative to a work station in a machine tool control system.

It is a more specific object of the present invention to provideimproved control of the reversing operation of a back gauge in a papercutting machine, or the like, wherein the back gauge is periodicallyreversed in its direction of movement pursuant to commands from 'acontrol record.

A still further object of the present invention is to provide improvedcircuit means for providing indications as to whether, in response to areverse mark, a movable member, such as a back gauge, should be drivenin a forward direction or a backward direction relative to a workstation.

A still further object of the present invention is to provide means sothat the forward most limiting marks recorded on different directioncommand channels of a control record need not be in alignment, while atthe same time preventing associated reversing circuitry from advancingthe movable member in a forward direction when a reverse sensor sensesthe forward most limiting reverse mark on the direction control channelfor a new program.

The foregoing and other objects and advantages of the invention willbecome more readily apparent from the following description of thepreferred embodiment of the invention taken in conjunction with theaccompanying drawings which are a part hereof and wherein:

FIG. 1 is a side view of a paper cutting machine to which the presentinvention may be applied;

FIG. 2 is a front elevational view showing a magnetic control recordhaving command marks magnetically recorded thereon together withmagnetic sensors for controlling the positioning and direction ofmovement of a back gauge relative to a cutting tool;

FIG. 3 is an enlarged perspective view of a portion of the controlrecord as well as the sensors shown in FIG. 2;

FIG. 4 is an enlarged schematic illustration of a portion of the controlrecord together with the sensors shown in FIGS. 2 and 3; and,

FIG. 5 is a combined schematic-block diagram illustration of the controlcircuitry employed in the present invention.

Referring now to the drawings wherein the showings are for purposes ofillustrating the preferred embodiment of the invention only and not forpurposes of limiting same, FIG. 1 illustrates a paper cutting machine CMincluding a table upon which a stack of material 12, such as paper, isplaced to be cut by a knife 14. During the cutting operation, material12 is held in place by a clamp 16. A back gauge 18, slideably movablealong table 10, serves to position the material 12 beneath the knife.Back gauge 18 is slideably moved along the surface of the table 10 in aforward direction toward knife 14, or in a backward direction away fromthe knife, by means of a lead screw 20 rotatably supported beneath thetable. Lead screw 20 may be turned to adjust the position of back gauge18 by means of a hand wheel 22. During normal operation, however, it iscontemplated that lead screw 20 be turned by means of a'dual speed,reversible direction, electric motor M for positioning the back gauge aswell as its direction of movement in dependence upon commands from aposition controller 26.

The position controller 26, as shown in FIGS. 2 and 3, includes acontrol record, such as record member 24, taking the form of a magnetictape formed into a continuous belt divided longitudinally throughout itslength by a plurality of evenly spaced sprocket holes 27. The recordmember 24 is reeved over sprocket wheels 28 and 30 so that the sprocketholes 27 mesh with teeth provided on the two sprocket wheels. Sprocketwheel 30 is driven by lead screw 20, as through a coupling chain 32, sothat record member 24 is driven in a direction and at a speed dependenton that of back gauge 18. Whereas record member 24 is illustrated asbeing driven at a speed having a 1:1 ratio with back gauge 18, it iscontemplated that speed reduction means may be provided so that thespeed relationship, while proportional, need not be at a 1:1 ratio.

Record member 24 may be divided into a large plurality of longitudinallyextending channels on which magnetic marks are recorded. The recordmember is divided longitudinally in half by sprocket holes 27 to definechannel sides 40 and 50. Channel side 40 may include the channels forstoring reverse marks to cause a change in the direction of travel ofback gauge 18, whereas channel side 50 may include channels on whichposition marks are recorded for purposes of causing positioning controlof back gauge 18. For purposes of simplifying the description of thepresent invention, channel side 40 is divided into two channels A and B,and channel side 50 is divided into two corresponding channels A and B'.One program will include two related channels, such as channel A andchannel A for a first program A-A', and channel B and channel B for asecond program B-B'. Three magnetic mark sensors are provided forsensing the magnetic marks. Sensor 52 is employed for purposes ofsensing direction command or reverse marks located in either channel Aor channel B, whereas sensors 54 and 56 serve to sense position commandmarks located in either channel A or channel B. The three sensors aremounted on a support 60 so as to be driven laterally relative to recordmember 24 by means of a motor 62 under the control of a suitable motorcontrol circuit 64. Thus, when it is desired to switch operations fromprogram A-A to program B43 the motor is energized so as to displacesupport 60 so that sensor 52 responds to reverse marks recorded inchannel B, and so that sensors 54 and 56 respond to position commandmarks recorded in channel B.

When the back gauge is being driven in its forward direction towardcutting tool 14, each position command mark for the program in operationis sequentially sensed first by sensor 54 and then by sensor 56. Sensor54 is typically known as the deceleration sensor since it serves toprovide a low speed control signal which through suitable circuitry (notshown) controls motor M to decelerate forward movement of the back gaugefrom a normal high speed to a low speed. When sensor 56, known as thestop sensor, senses the same mark it provides a stop signal whichthrough suitable circuitry (not shown) controls motor M to decelerateforward movement of the back gauge from the low speed to a stopcondition at which time a cutting operation is performed. Between therearward most and forward most travel positions of back gauge 18 acutting program may require the back gauge to be stopped at a pluralityof positions in dependence upon the position command marks recorded onchannel A or channel B. The forward most limiting position desired forthe forward travel of back gauge 18 for a particular program is definedby a reverse mark located on channel A or B, depending on the programinvolved. The rearward most limiting position desired for the backwardtravel of back gauge 18 is defined by another reverse mark recorded onchannel A or B, depending on the program employed. For example, withreference to FIG. 3, reverse mark 70 in channel A is representative ofthe desired rearward most position of back gauge 18 for program A-A'.The forward most limiting position for this program may be representedby reverse mark 72 located in channel A. Within the confines of thistravel distance various stop defining positions for back gauge 18 areprovided by position command marks 74 located in channel A.

During the operation of the cutting machine pursuant to program A-A',motor M will drive back gauge 18 in a forward direction toward cuttingtool 14 and thereby cause record member 24 to be driven in its forwarddirection, as indicated by arrow 80 in FIG. 3. On the assumption thatmark 70 is located in advance of sensor 52, then sensors 54 and 56 willsequentially sense each mark 74 so that back gauge 18 is firstdecelerated to a low speed and then decelerated to a stop condition atwhich time a cutting operation is performed. After the last positioncommand mark 74 has been sensed a trailing reverse mark, in this casemark 72, will be sensed by reverse sensor 52. The reverse sensordevelops a reverse signal pulse which is applied to a program controlcircuit, to be described in greater detail hereinafter, for purposes ofreversing the operation of motor M so that back gauge 18 and, hence,record member 24 are driven in a backward direction. As the recordmember is driven in the backward direction, sensors 54 and 56 do notrespond to position marks 74 for purposes of decelerating and thenstopping movement of back gauge 18. However, as the back gauge is movedto the desired rearward most position for cutting program A-A, sensor 52will sense reverse mark 70 to produce a reverse signal pulse which isapplied to the program control circuit to reverse the direction oftravel of back gauge 18 sothat it will now travel in a forwarddirection.

in accordance with the present invention, the output signal pulsesdeveloped by the reverse sensor 52 and the stop sensor 56 are applied toa program control circuit CC for purposes of controlling a conventionalmotor control circuit MC to control motor M to drive back gauge 18 ineither the forward or backward directions. Within control circuit CC, asshown in FIG. 5, the stop sensor 56 has its output circuit connected toa channel centering logic circuit CL and the output circuit of reversesensor 52 is connected to a'reversing logic circuit RL.

In a broad sense, the reversing logic circuit serves to control themotor so as to drive the back gauge 18 in either the forward directionor in the backward direction in dependence upon the direction the backgauge was proceeding at the point in time a reverse mark is sensed. Thecentering logic circuit CL prevents the back gauge from being reversedin its direction of travel from its backward direction to its forwarddirection in response to a reverse mark being sensed until a positionmark is sensed by sensor 56.

The channel centering logic circuit CL includes a stop amplifier 90 ofconventional design having its input circuit connected to the outputcircuit of stop sensor 56. The stop signal pulse, as amplified byamplifier 90, is then shaped by a suitable pulse shaping circuit 92 toprovide a positive or binary 1" signal pulse of a given magnitude andduration. This binary l signal is applied to both inputs of an NAND gate94, serving as an inverter amplifier, to produce a binary 0" signal foreach position mark sensed by stop sensor 56. The output circuit takenfrom NAND gate 94 is applied as one input to a NAND gate 96, which isconnected together with an additional NAND gate 98 to define a bistablemultivibrator or flip flop 100. The second input of NAND gate 98 isobtained from the reverse logic circuit RL through normally open relaycontacts FR-l. The output of flip-flop 100 is taken from the outputcircuit of NAND gate 96 and applied to an inverter amplifier 102 whoseoutput circuit is, in turn, connected through a relay coil L to ground.Consequently, whenever the output of flip-flop 100 is a binary "0"signal, relay coil L is energized to open its normally closed relaycontacts L-l. So long as relay coil L is deenergized, relay contactsL--] are closed. Relay contacts L-l are located in the reverse logiccircuit RL and, when open, serve to prevent a reverse signal pulsedeveloped by reverse sensor 52 from being processed by the reverse logiccircuit RL. A manual reset is provided for deenergizing the coil L. Thereset is obtained with a NAND gate having its output circuit connectedto one of the input circuit of NAND gate 96. Upon closure of a switch97, binary l signals are applied to NAND gate 95, causing the outputcircuit of flipflop to carry a binary l signal and thereby deenergizerelay coil L.

The reversing logic circuit RL basically includes a back gauge directionmemory in the form of a J-K flip-flop FF-l, a memory driving circuit MDand motor direction command controls in the form of a forward to reverserelay coil FR and a reverse to forward relay coil RF. When coil FR ismomentarily energized a command is given to change the direction oftravel of the back gauge from its forward direction to its backwarddirection. When relay coil RF is momentarily energized a command isgiven to drive the back gauge in the forward direction. A momentaryenergization of the forward to reverse relay coil FR, as will bedescribed in greater detail hereinafter, causes a motor reverse relaycoil R to be energized to close its normally open relay contacts R--] tooperate a conventional motor control circuit MC to control motor M todrive back gauge 18 in the backward direction. Similarly, whenever thereverse to forward coil RF is momentarily energized it causes a motorforward relay coil F to become energized to close its normally openrelay contacts F4 to operate the motor control circuit MC to controlmotor M to drive back gauge 18 in the forward direction.

The memory drive circuit MD includes a pair of normally open reverserelay contacts R-2 and a pair of normally closed reverse relay contactsR-3, both operated by the reverse relay coil R. These contacts areconnected together in series with the junction thereof being connectedto ground. Contacts R-2 provide a circuit between ground and one inputof a NAND gate and relay contacts R-3 provide a circuit between groundand one input of NAND gate 112. NAND gates 110 and 112 are connectedtogether to define a bistable multivibrator circuit which is used as aconventional relay antibounce flip-flop circuit. The output of NAND gate112 is connected in series with normally open relay contacts FR-l to oneinput of NAND gate 98 in the center logic circuit CL.

If the back gauge is traveling in the forward direction then relay coilR is deenergized. Consequently, its relay contacts R-3 are closed andthe output circuit of NAND gate 112 carries a binary l signal. If atthis point in time the forward to reverse coil FR is momentarilyenergized, to command movement in a backward direction, then its relaycontacts F R-l will momentarily close. But, relay coil FR is energizedlong enough for relay coil R to become energized and thereby cause itscontacts R-3 to open. Thus, NAND gate 112 applies a binary 0 signalpulse through contacts FR-l to NAND gate 98. If at this point in timestop sensor 56 is not sensing a position command mark, then NAND gate 94applies a binary 1" signal to the other input of NAND gate 96.Consequently, the output circuit of NAND gate 96 carries a binary 0signal which is inverted by inverter amplifier 102 to energize relaycoil L. This causes relay contacts L-l to open so that as the back gaugestarts to travel in the backward direction, the reverse sensor 52 willnot be effective. This condition will prevail until stop sensor 56senses a position command mark at which time NAND gate 94 applies abinary 0" signal to NAND gate 96 to cause relay coil FL to bedeenergized. Thereafter, the next reverse mark sensed by reverse sensor52 will be effective to cause reversal of the direction of the movementof back gauge 18.

The output circuit of reverse sensor 52 is coupled to a conventionalamplifier which applies the amplified signal through normally closedrelay contacts L-l to a time delay pulse shaping circuit 122. Circuit122 serves upon receipt of each reverse signal pulse to provide anelongated signal pulse which has a time duration in excess of the timerequired for a mark to be sensed by reverse sensor 52 and thenretraversed passed the sensor. Thus, circuit 122 provides only a singlepulse each time a mark is sensed by sensor 52. The output of pulseshaping circuit 122 is applied to another pulse shaping circuit 124 thatserves to provide a trigger pulse of substantially shorter duration thanthe pulse provided by shaping circuit 122 and at substantially at thepoint in time corresponding with the leading edge of the pulse providedby circuit 122. This trigger pulse is applied to the trigger input ofthe J-K flipflop FF-l.

Flip-flop FF-l, in a conventional fashion, includes first and secondinput circuits X and Y and corresponding output circuits X and Y. As iswell known, once a trigger pulse is applied to input trigger circuit Tthe pattern of binary signals on input circuits X and Y is transferredto output circuits X and Y. Input circuit Y is directly connected to theoutput circuit of NAND gate 110. Input circuit X is connected to theoutput circuit of a NAND gate 126 having both its input circuitsconnected to the output circuit of NAND gate 110. Hence, NAND gate 126merely serves as an inverter amplifier. Output circuit X is connected toone input circuit of a NAND gate 128, whereas output circuit Y isconnected to one input circuit of NAND gate 130. The second inputcircuit of NAND gate 128 is connected to the output circuit of pulseshaper circuit 122 through a resistor 132. Similarly, the second inputcircuit of NAND gate 130 is connected to the output circuit of pulseshaping circuit 122 through a resistor 134. An inverter amplifier 136 isconnected between the output circuit of NAND gate 128 and the base of anNPN transistor 140 having its collector connected to a B+ voltage supplysource and its emitter connected through relay coil FR to ground.Similarly, an inverter amplifier 142 connects the output circuit of NANDgate 130 to the base of an NPN transistor 144 having its collectorconnected to a 8+ voltage supply source and its emitter connectedthrough the reverse to forward relay coil RF.

The forward to reverse relay coil FR and the reverse to forward relaycoil RF are respectively energized for momentary time durationsdependent upon the time duration of a gating pulse provided by shapingcircuit 122. When relay coil FR is momentarily energized it isindicative that the back gauge is traveling in the forward direction andit is now to reverse its direction and proceed in the forward direction.Conversely, when the reverse to forward relay coil RF is momentarilyenergized it is indicative that the back gauge is traveling in thebackward direction and should now proceed to travel in the forwarddirection.

When relay RF is momentarily energized its normally open relay contactsRF-l become closed to complete a circuit between a 8+ voltage supplysource and ground through a holding relay coil A. Consequently, normallyopen relay contacts A-l of the holding relay become closed to maintaincoil A energized through normally closed relay contacts FR-l. Inaddition, during the period that relay coil RF is energized its normallyclosed contacts RF-2 become open to deenergize reverse relay coil R.Consequently, normally closed reverse relay contacts R-S become closedso that the forward relay coil becomes energized. When relay coil F isenergized, its normally closed relay contacts F-2 open to preventre-energization of relay coil R and its normally open contacts F-lbecome closed so that motor M is operated to drive the back gauge in theforward direction.

When the forward to reverse relay coil FR is momentarily energized itsnormally closed relay contacts FR-l open to break the holding circuitand thereby deenergize relay coil A as well as the forward relay coil F.Consequently, the normally closed forward relay contacts F-2 becomeclosed. Since relay coil FR is energized for a period of time sufficientfor relay contacts F-2 to become closed, a circuit is now'completedthrough relay contacts FR-2 to energize the reverse relay coil R. Oncerelay coil R is energized its normally open contacts R4 become closed tocomplete a holding circuit through normally closed contacts RF-2 aroundrelay contacts FR-2.

Reference is now made both to FIGS. 4 and 5 in conjunction with theoperation which ensues first with the back gauge 18 traveling in aforward direction and then when it is reversed and driven in a backwarddirection. As back gauge 18 is driven in the forward direction, recordmember 24 is driven at a proportional velocity in the same direction.Consequently, each position command mark 74 is sensed first bydeceleration sensor 54 and then by stop sensor 56 to respectivelyprovide deceleration and stop control signals so that suitable circuitry(not shown) serves for each sensed mark to first decelerate the backgauge from a high speed to a low speed and then decelerate the backgauge from the low speed to a stop condition. After the last positioncommand mark 74 has been sensed by sensors 54 and 56, the forwardlimiting mark 72 will be sensed by reverse sensor 52. The reverse sensor52 develops a reverse signal pulse which is amplified by amplifier andapplied through normally closed relay contacts L-l to the time delaypulse shaping circuit 122. Since the back gauge has been traveling inits forward direction, relay coil R is not energized, and, consequently,its normally open contacts R-2 are open and its normally closed contactsR-3 are closed. The pulse shaping circuit 124 applies a trigger pulse inresponse to the leading edge of the time delay pulse from shapingcircuit 122 to the trigger circuit T of flip-flop FF-l. Since relaycontacts R-2 are open, the output circuit of NAND gate 110 carries abinary 0 signal. Consequently, a binary 1 signal is present on inputcircuit X and a binary 0 signal is present on input circuit Y offlip-flop FF-l.

In response to the trigger pulse applied to trigger circuit T, outputcircuit X will now carry a binary 1 signal and output circuit Y willcarry a binary 0" signal. The elongated output signal pulse from shapingcircuit 122 is applied to one input each of NAND gates 128 and 130, and,hence, for the time duration of that signal pulse transistor and relaycoil FR are energized. As previously described, this will cause theforward relay coil F to be deenergized and the reverse relay coil tobecome energized. When relay coil R is energized its normally opencontacts R-2 close and its normally closed contacts R-3 open so thatinput circuit X of flip-flop FF-l now carries the binary 0" signal,whereas input circuit Y now carries a binary l signal. This, however,will not affect the condition of output circuits X and Y whichrespectively carry binary l and binary 0" signals since the triggerpulse applied to trigger circuit T was of a shorter time duration thanthat required for relay coil R to become energized. This will preventthe flipflop circuit from oscillating during the reversing operation andthereby accurately control the reversing operation of back gauge 18.

At this point in the operation of cutting machine CM, the operator maydecide to shift to a new program, such as program B-B'. From FIG. 4 itwill be noted that the forward travel limiting reverse mark of channel Bis not aligned with the forward travel limiting reverse mark 72 inchannel A. To the contrary, mark 150 is located in advance of mark 72 bya distance greater than the over travel distance normally compensatedfor by the time delay pulse shaping circuit 122, described in detailhereinbefore. This means that as record member 24 starts to move in thebackward direction, direction command mark 150 will be located inadvance of sensor 52, as shown by the dotted lines 150'. Since thesensors will all be displaced to sense the marks in channels B and B,the reverse sensor 52 will develop a reverse signal in response tosensing mark 150. If the back gauge is now reversed in its direction oftravel, it will be trapped in advance of its forward most limitingposition for program 8-8. The problem may be obviated by aligning marks72 and 150. However, this would require substantial programming timewhen recording the programs. It is preferable that reverse sensor 52 be,in effect, deactivated so as to not sense a reverse mark in channel Buntil the back gauge is driven to its rearward most limiting position,as denoted by mark 152. This function is accomplished by the channelcentering logic circuit CL which requires that when programs arechanged, such as from program A-A to program 3-3, a reverse signal pulsefrom sensor 52 will not be effective until stop sensor 56 has sensed oneof the position command marks 154 on channel B.

As the back gauge is driven in its backward direction, and prior to aposition mark being sensed by stop sensor 56, relay coil L will beenergized, as has been described in detail hereinbefore. Consequently,when mark 150 is sensed by reverse sensor 52 its output signal pulse asamplified by amplifier 120 will not be applied to the time delay pulseshaping circuit 122. Therefore, the reverse logic circuit RL isineffective to respond to the reverse signal pulse. As the back gaugeroceeds in its backward direction, stop sensor 56 will sense the firstposition command mark 154 on channel B. The stop sensor develops a stopsignal pulse which is amplified and shaped to cause binary l signals tobe applied to both input circuits of NAND gate 94. Thus, NAND gate 94will now apply a binary signal to NAND gate 96 causing its outputcircuit to carry a binary 1 signal and thereby deenergize relay coil L.Relay contacts L-l will now close so that the relay logic circuit RLwill respond to the next reverse mark sensed by reverse sensor 52.

The back gauge will continue to move in its backward direction untilreverse sensor 52 senses reverse mark 152 in channel B. Reverse sensor52 develops a reverse signal pulse which is applied to the time delaypulse shaping circuit which, as described in greater detailhereinbefore, will cause relay coil RF to become momentarily energizedso as to control motor M to drive the back gauge in the forwarddirection. Back gauge 18 will now proceed toward the cutting tool 14 andcutting operations will be performed in dependence upon position commandmarks 154.

The invention has been described with reference to a preferredembodiment, however, it is to be appreciated that the invention is notlimited to same as various modifications may be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

What is claimed is:

1. In a machine control system for controlling the positioning anddirection of travel of a movable member driven by a reversible motor ineither a forward or backward direction relative to a work station independence upon an operating program and comprising:

a control record having command marks recorded thereon including aposition channel having position command marks to define desiredpositions of said movable member relative to said work station and anassociated direction channel having two direction reverse command marksrecorded thereon at spaced locations defining the beginning and endingprogram boundaries of the associated position channel;

position mark sensor means and reverse mark sensor means forrespectively sensing said position marks and reverse marks and providingfor each respectively sensed mark a position signal pulse and a reversesignal pulse;

means for imparting relative motion between said control record and saidsensor means in dependence upon the forward and backward directions oftravel of said movable member relative to said work station;

reverse control circuit means for normally responding to each saidreverse signal pulse for controlling said motor to reverse the directionof travel of said member;

means for providing an indication representative that a sensed reversemark commanded said member to change its direction of travel fromforward to backward; and

control circuit means responsive to said indication to prevent saidreverse control circuit means from responding to a said reverse markuntil said position sensor means senses a said position mark.

2. In a machine control system as set forth in claim 1, wherein saidrecord member is provided with a plurality of associated said positionand direction channels for different operating programs.

3. In a machine control system as set forth in claim 2, including meansfor adjustably positioning said position and said reverse mark sensormeans to respond to position and reverse marks of a selected one of saidprograms.

4. In a machine control system as set forth in claim 3, wherein saiddifferent position channels each have a forward most defining reversemark and a said rearward most defining reverse mark, each said forwardmost defining reverse mark being recorded at a location on said controlrecord so as to be representative of a desired forward most position ofsaid movable member for the associated program and located independentlyof a forward most defining reverse mark as sociated with a differentprogram.

5. In a machine control system as set forth in claim 1, wherein saidreverse control circuit means includes direction command means forproviding a forward to reverse command signal pulse each time saidreverse control circuit means responds to a said reverse mark when saidmovable member is traveling in a forward direction.

6. In a machine control system as set forth in claim 5, wherein saidindication providing means includes switching means having a normalfirst condition and controlled by said direction command means so as tobe at least momentarily actuated to a second condition for each saidcommand signal pulse.

7. In a machine control system as set forth in claim 6, includingcircuit means for providing a distinctive signal when said movablemember is traveling in said backward direction;

said control circuit means including bistable means having a normalfirst condition and being actuated to a second condition in response toreceiving a said distinctive signal when said switching means isactuated to its second condition.

8. In a machine control system as set forth in claim 7, including sensordisconnecting means for disconnecting said reverse sensor means fromsaid reverse control circuit means when said bistable means is in itssecond condition.

9. In a machine control system as set forth in claim 8, wherein saidcontrol circuit means includes stop signal circuit means interposedbetween said stop sensor means and said bistable means to actuate saidbistable means from its second condition to its first condition inresponse to a said stop signal pulse, whereby said reverse sensor meansis reconnected to said reverse control circuit means.

10. In a machine control system for reversing the direction of travel ofa movable member driven by reversible motor means between forward mostand rearward most positions relative to a work station and comprising:

a control record having two spaced reverse marks recorded thereon fordefining said forward most and rearward most positions;

reverse sensor means for sensing said marks and providing a reversesignal pulse in response to each mark sensed;

means for imparting relative motion between said control record and saidsensor means in dependence upon the forward and backward directions oftravel of said movable member relative to said work station;

direction memory means having input and output circuits and a triggerpulse receiving circuit and exhibiting the characteristic of beingactuated by a received trigger pulse to first and second stable stateoutput circuit conditions in respective dependence upon first and secondinput circuit conditions existing when a trigger pulse is received;

means for applying a said trigger pulse to said memory means in responseto each said reverse signal pulse;

direction command means controlled by said memory means to control saidreversible motor means to drive said member in the backward directioneach time said memory means is actuated to its first output circuitcondition and in the forward direction each time said memory means isactuated to its second output circuit condition; and

memory input conditioning means for conditioning said memory inputcircuit to its second condition when said member is traveling in saidbackward direction and to said first condition when said member istraveling in said forward direction.

1 1. In a machine control system as set forth in claim 10, includingtime delay means interposed between said reverse sensor means and saidtrigger pulse means for providing, for each said reverse signal pulse, atime delay control pulse having a time duration substantially in excessof a said trigger pulse and greater than the time period required forsaid movable member to first over travel a said forward most or rearwardmost position and retraverse passed said position so that a single saidcontrol pulse is provided for each said mark during a reversingoperation.

12. In a machine control system as set forth in claim 11, includinggating means interposed between said direction command means and saidmemory means so that said direction command means is controlled by saidmemory means for a time duration dependent upon that of said controlpulse.

13. In a machine control system as set forth in claim 12, wherein saidtrigger pulse means provides a said trigger pulse at a point in timeessentially corresponding with the leading edge of said control pulseand of sufficiently short duration so that upon termination of a saidtrigger pulse said memory means is actuated to one of its said outputconditions before its input circuit condition is changed.

14. In a machine control system as set forth in claim 10, wherein saiddirection memory means includes first and second said input circuits forreceiving a first and second pattern of binary signals respectivelyrepresentative of said first and second input conditions, and first andsecond said output circuits for carrying said first and said secondpatterns of binary signals respectively representative of said first andsecond conditions.

15. In a machine control system as set forth in claim 14, wherein saidmemory input conditioning means includes circuit means for applying asaid first pattern of binary signals to said first and second memoryinput circuits when said movable member is traveling in said forwarddirection and a said second pattern of binary signals thereto when saidmovable member is traveling in said backward direction.

16. In a machine control system as set forth in claim 10, wherein saidcontrol record has at least one position mark recorded thereon;

position sensor means for sensing a said position mark;

means for providing an indication that a said sensed reverse markcommanded reverse movement of said movable member from said forwarddirection to said backward direction; and

control circuit means responsive to said indication to prevent saidtrigger pulse means from responding to a said reverse signal pulse untilsaid position mark is sensed by said position sensor means.

17. In a method of operating a linearly movable member over differentlinear distances in opposite directions in accordance with differentselective pre-established programs, wherein said programs are carried bya record member and each program includes at least one stop signal forcontrolling an intermediate stop position of the member when moving inone direction and a reverse signal at each end of each program beyondthe extremities of stop signals contained therein, and wherein signalsensing means is provided to sense stop and reverse signals on therecord member for controlling the movable member, said means beingproportionately movable relative to said record member in response tomovement of said linearly movable member, the improvement comprising thesteps of:

a. moving said movable member in said one direction and intermittentlystopping said member in response to sensing of each stop signal in afirst program,

b. sensing a reverse signal beyond the last stop signal in said firstprogram and then: l. reversing the direction of travel of said movablemember,

2. selecting a second program and sensing for a stop signal thereinduring said reverse travel,

3. inhibiting a said stop signal in said second program from stoppingsaid movable member during said reverse travel, and

4. inhibiting said sensing means from responding to a said reversesignal,

c. reinstating the operability of said sensing means to respond to asaid reverse signal upon receipt by said sensing means of a stop signalwhile said member is travelling in said reverse direction,

d. reversing the direction of travel of said movable member in responseto sensing a reverse signal at the extremity of said second program tocause said member to again travel in said one direction, and

e. stopping said movable member in response to a said stop signal insaid second program.

1. In a machine control system for controlling the positioning anddirection of travel of a movable member driven by a reversible motor ineither a forward or backward direction relative to a work station independence upon an operating program and comprising: a control recordhaving command marks recorded thereon including a position channelhaving position command marks to define desired positions of saidmovable member relative to said work station and an associated directionchannel having two direction reverse command marks recorded thereon atspaced locations defining the beginning and ending program boundaries ofthe associated position channel; position mark sensor means and reversemark sensor means for respectively sensing said position marks andreverse marks and providing for each respectively sensed mark a positionsignal pulse and a reverse signal pulse; means for imparting relativemotion between said control record and said sensor means in dependenceupon the forward and backward directions of travel of said movablemember relative to said work station; reverse control circuit means fornormally responding to each said reverse signal pulse for controllingsaid motor to reverse the direction of travel of said member; means forproviding an indication representative that a sensed reverse markcommanded said member to change its direction of travel from forward tobackward; and control circuit means responsive to said indication toprevent said reverse control circuit means from responding to a saidreverse mark until said position sensor means senses a said positionmark.
 2. selecting a second program and sensing for a stop signaltherein during said reverse travel,
 2. In a machine control system asset forth in claim 1, wherein said record member is provided with aplurality of associated said position and direction channels fordifferent operating programs.
 3. In a machine control system as setforth in claim 2, including means for adjustably positioning saidposition and said reverse mark sensor means to respond to position andreverse marks of a selected one of said programs.
 3. inhibiting a saidstop signal in said second program from stopping said movable memberduring said reverse travel, and
 4. inhibiting said sensing means fromresponding to a said reverse signal, c. reinstating the operability ofsaid sensing means to respond to a said reverse signal upon receipt bysaid sensing means of a stop signal while said member is travelling insaid reverse direction, d. reversing the direction of travel of saidmovable member in response to sensing a reverse signal at the extremityof said second program to cause said member to again travel in said onedirection, and e. stopping said movable member in response to a saidstop signal in said second program.
 4. In a machine control system asset forth in claim 3, wherein said different position channels each havea forward most defining reverse mark and a said rearward most definingreverse mark, each said forward most defining reverse mark beingrecorded at a location on said control record so as to be representativeof a desired forward most position of said movable member for theassociated program and located independently of a forward most definingreverse mark associated with a different program.
 5. In a machinecontrol system as set forth in claim 1, wherein said reverse controlcircuit means includes direction command means for providing a forwardto reverse command signal pulse each time said reverse control circuitmeans responds to a said reverse mark when said movable member istraveling in a forward direction.
 6. In a machine control system as setforth in claim 5, wherein said indication providing means includesswitching means having a normal first condition and controlled by saiddirection command means so as to be at least momentarily actuated to asecond condition for each said command signal pulse.
 7. In a machinecontrol system as set forth in claim 6, including circuit means forproviding a distinctive signal when said movable member is traveling insaid backward direction; said control circuit means including bistablemeans having a normal first condition and being actuated to a secondcondition in response to receiving a said distinctive signal when saidswitching means is actuated to its second condition.
 8. In a machinecontrol system as set forth in claim 7, including sensor disconnectingmeans for disconnecting said reverse sensor means from said reversecontrol circuit means when said bistable means is in its secondcondition.
 9. In a machine control system as set forth in claim 8,wherein said control circuit means includes stop signal circuit meansinterposed between said stop sensor means and said bistable means toactuate said bistable means from its second condition to its firstcondition in response to a said stop signal pulse, whereby said reversesensor means is reconnected to said reverse control circuit means. 10.In a machine control system for reversing the direction of travel of amovable member driven by reversible motor means between forward most andrearward most positions relative to a work station and comprising: acontrol record having two spaced reverse marks recorded thereon fordefining said forward most and rearward most positions; reverse sensormeans for sensing said marks and providing a reverse signal pulse inresponse to each mark sensed; means for imparting relative motionbetween said control record and said sensor means in dependence upon theforward and backward directions of travel of said movable memberrelative to said work station; direction memory means having input andoutput circuits and a trigger pulse receiving circuit and exhibiting thecharacteristic of being actuated by a received trigger pulse to firstand second stable state output circuit conditions in respectivedependence upon first and second input circuit conditions existing whena trigger pulse is received; means for applying a said trigger pulse tosaid memory means in response to each said reverse signal pulse;direction command means controlled by said memory means to control saidreversible motor means to drive said member in the backward directioneach time said memory means is actuated to its first output circuitcondition and in the forward direction each time said memory means isactuated to its second output circuit condition; and memory inputconditioning means for conditioning said memory input circuit to itssecond condition when said member is traveling in said backwarddirection and to said first condition when said member is traveling insaid forward direction.
 11. In a machine control system as set forth inclaim 10, including time delay means interposed between said reversesensor means and said trigger pulse means for providing, for each saidreverse signal pulse, a time delay control pulse having a time durationsubstantially in excess of a said trigger pulse and greater than thetime period required for said movable member to first over travel a saidforward most or rearward most position and retraverse passed saidposition so that a single said control pulse is provided for each saidmark during a reversing operation.
 12. In a machine control system asset forth in claim 11, including gating means interposed between saiddirection command means and said memory means so that said directioncommand means is controlled by said memory means for a time durationdependent upon that of said control pulse.
 13. In a machine controlsystem as set forth in claim 12, wherein said trigger pulse meansprovides a said trigger pulse at a point in time essentiallycorresponding with the leading edge of said control pulse and ofsufficiently short duration so that upon termination of a said triggerpulse said memory means is actuated to one of its said output conditionsbefore its input circuit condition is changed.
 14. In a machine controlsystem as set forth in claim 10, wherein said direction memory meansincludes first and second said input circuits for receiving a first andsecond pattern of binary signals respectively representative of saidfirst and second input conditions, and first and second said outputcircuits for carrying said first and said second patterns of binarysignals respectively representative of said first and second conditions.15. In a machine control system as set forth in claim 14, wherein saidmemory input conditioning means includes circuit means for applying asaid first pattern of binary signals to said first and second memoryinput circuits when said movable member is traveling in said forwarddirection and a said second pattern of binary signals thereto when saidmovable member is traveling in said backward direction.
 16. In a machinecontrol system as set forth in claim 10, wherein said control record hasat least one position mark recorded thereon; position sensor means forsensing a said position mark; means for providing an indication that asaid sensed reverse mark commanded reverse movement of said movablemember from said forward direction to said backward direction; andcontrol circuit means responsive to said indication to prevent saidtrigger pulse means from responding to a said reverse signal pulse untilsaid position mark is sensed by said position sensor means.
 17. In amethod of operating a linearly movable member over different lineardistances in opposite directions in accordance with different selectivepre-established programs, wherein said programs are carried by a recordmember and each program includes at least one stop signal forcontrolling an intermediate stop position of the member when moving inone direction and a reverse signal at each end of each program beyondthe extremities of stop signals contained therein, and wherein signalsensing means is provided to sense stop and reverse signals on therecord member for controlling the movable member, said means beingproportionately movable relative to said record member in response tomovement of said linearly movable member, the improvement comprising thesteps of: a. moving said movable member in said one direction andintermittently stopping said member in response to sensing of each stopsignal in a first program, b. sensing a reverse signal beyond the laststop signal in said first program and then: